STUART, CHARLES, sixth Duke of Lennox and third Duke of Richmond (1640–1672), born in London on 6 Mar. 1639–40, was the only son of George Stuart, ninth seigneur d'Aubigny, who was fourth son of Esmé, third duke of Lennox [see under Stuart, Ludovick, second Duke of Lennox]. Charles Stuart's mother was Catherine Howard (d. 1650), eldest daughter of Theophilus, second earl of Suffolk, who, after the death of her husband, George Stuart, at Edgehill in 1642, married Sir James Levingstane, created Earl of Newburgh in 1660.

On 10 Dec. 1645 Charles was created Baron Newbury and Earl of Lichfield, titles intended for his uncle, Bernard Stuart (1623?–1646) [q. v.] In January 1658 he crossed to France, and took up his residence in the house of his uncle, Ludovic, seigneur d'Aubigny (Cal. State Papers, Dom. 1657–8, pp. 264, 315, 512, 551). In the following year he fell under the displeasure of the council of state, and warrants were issued for seizing his person and goods (ib. 1559–60, pp. 98, 227, 229). This wounded him deeply, and when, after the Restoration, he sat in the Convention parliament, he showed great animosity towards the supporters of the Commonwealth.

He returned to England with Charles II, and on the death of his cousin, Esmé Stuart, on 10 Aug. 1660, he succeeded him as Duke of Richmond and Lennox [see under Stuart, James, fourth Duke of Lennox and first Duke of Richmond]. In the same year he was created hereditary great chamberlain of Scotland, hereditary great admiral of Scotland, and lord-lieutenant of Dorset. On 15 April 1661 he was invested with the order of the Garter, and in 1662 he joined Middleton in Scotland, where, according to Burnet, his extravagances and those of his stepfather, the Earl of Newburgh, did much to discredit the lord high commissioner.

The Duke of Richmond was an insatiable petitioner for favours from the crown, and, although he did not obtain all he desired, he was one of those who benefited most largely by Charles's profusion (Cal. State Papers, Dom. 1660–71, passim). Among other grants, on 28 April 1663 he received a pension of 1,000l. a year as a gentleman of the bedchamber (ib. 1663–4, pp. 89, 121). The sun of the royal favour was, however, sometimes obscured, for in 1665 he was incarcerated in the Tower from 30 March to 21 April on account of a difference with the king (ib. 1664–5, pp. 280, 281, 322). On the death of his uncle, Ludovic Stuart, he succeeded him as Seigneur D'Aubigny, and did homage by proxy to Louis XIV on 11 May 1670. On 28 May 1666 he received the grant for himself and his heirs male of the dignity of Baron Cobham, and on 2 July, when the country was alarmed by the presence of the Dutch in the Thames, he was appointed to the command of a troop of horse (ib. 1665–1666, pp. 417, 489). In July 1667, by the death of his cousin, Mary Butler, countess of Arran, he became Lord Clifton de Leighton-Bromswold [see Stuart, Bernard, titular Earl of Lichfield], and on 4 May 1668 he was made lord lieutenant and vice admiral of Kent jointly with the Earl of Winchilsea (ib. 1667–8, pp. 364, 374, 398).

Shortly before this the duke had taken a step which shook him very much in the king's favour—his marriage, namely, in March 1667, with Charles's innamorata, ‘La Belle Stuart’ [see Stuart or Stewart, Frances Teresa]. Richmond suffered less for his temerity than might have been anticipated, which is easily explicable if Lord Dartmouth's assertion be true, that ‘after her marriage she had more complaisance than before, as King Charles could not forbear telling the Duke of Richmond when he was drunk at Lord Townshend's in Norfolk.’

In 1671 he was sent as ambassador to the Danish court to persuade Denmark to join England and France in the projected attack on the Dutch. He died at Elsinore on 12 Dec. 1672, and was buried in Westminster Abbey on 20 Sept. 1673 (Brit. Mus. Addit. MS. 6292, f. 16). He was thrice married, but had no children. His first wife, Elizabeth, was the eldest daughter and coheiress of Richard Rogers of Bryanstone, Dorset, and the widow of Charles Cavendish, styled Viscount Mansfield. She died in childbed on 21 April 1661, and he married secondly, on 31 March 1662, Margaret, daughter of Laurence Banister of Papenham, Buckinghamshire, and widow of William Lewis of Bletchington, Oxfordshire. She died in December 1666, and in March 1666–7 he married Frances Teresa Stewart. By the duke's death all his titles became extinct, except the barony of Clifton of Leighton-Bromswold, which descended to his sister Katherine. Charles II, however, though not lineally descended from any of the dukes of Lennox or Richmond, yet as their nearest collateral heir male was by inquisition post mortem, held at Edinburgh on 6 July 1680, declared the nearest heir male (Chancery Records, Scotland, vol. xxxvii. f. 211; ap. Stuart, Genealog. Hist. 1798, pp. 281–3). These titles, having reverted to the king, were bestowed by him in August 1675 on his natural son Charles Lennox, first duke of Richmond [q. v.] The duke's will, dated 12 Jan. 1671–2, was proved on 14 Feb. 1672–3, and is printed in the ‘Archæologia Cantiana’ (xi. 264–71).

‘An Elegie on his Grace the illustrious Charles Stuart’ was published in the year of his death, but is a work of slight merit. Five volumes of his letters and papers are among the additional manuscripts in the British Museum (Addit. MSS. 21947–51).